[The behavior of free thyroxine and triiodothyronine concentrations after short-term balanced inhalation anesthesia]

Acute changes involving the hormones thyroxine (T4) and triiodothyronine (T3) followed by hyper -or hypothyroid crises will lead to both cardiovascular and metabolic disorders. Due to highly sensitive mechanisms controlling central hormonal production and peripheral enzymatic conversion (c.g. T4 to T3), numerous pharmacologically effective substances will influence the kinetics of these hormones. Thus, agents routinely used in anesthetic practice and their metabolites may disturb hormonal regulation in particular due to their central effectiveness [1, 2,5-7]. Based on this premise, it was our goal to search for anesthetic-induced hormonal changes in euthyroid patients living in a goiter-endemic area scheduled for short, elective orthopedic operations. Investigations were done in 21 outpatients (mean age: 24 years, mean body wt.: 64 kg) undergoing minor surgical procedures of the extremities. No clinical signs of thyroid disturbances could be observed preoperatively in the patients. Immediately after intravenous premedication (meperidine HCl 0.75 mg/kg and atropine 0.25 mg), anesthesia was induced (thiopentone 5 mg/kg) and continued by inhalation via face; mask using volatile agents: halothane, isoflurane, or enflurane (O2: N2O; FiO2 = 0.33). According to the anesthetic agent administered (halothane, isoflurane, enflurane), patients were divided into three groups of 7 patients each as listed in Table 1. Blood samples to determine free serum T4 (fT4) and T3 (fT3) as an expression of biologically available T4/T3, unconjugated to transport globulins, were drawn twice: immediately before premedication; and postoperatively after the patient had regained consciousness.(ABSTRACT TRUNCATED AT 250 WORDS)